794
FXUS63 KMQT 251944
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
344 PM EDT Sat May 25 2024

.KEY MESSAGES...

- Approaching low pressure system brings isolated shower or
  thunderstorm chances to the far west this evening.

- Approaching low pressure system brings widespread rain chances
late Sunday into early Monday. Rainfall amounts >1 inch are possible
by Monday evening.

- Below normal temperatures for the first half of the week, followed
by a drying trend midweek. Patchy frost possible Thursday morning.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 240 AM EDT Sat May 25 2024

Upper air pattern consists of a 500 mb closed low near Lake Winnipeg
this morning which meanders slowly northwest into western Ontario by
00z Sun. There is some 850-500 mb q-vector convergence and some
moisture that comes into the west late in the day while earlier
moisture and q-vector convergence moves out across the cwa this
morning. Showers will continue to move out this morning and then the
next wave comes into the far west by late this afternoon. Appears
like this next wave would be in the southern part of a deformation
zone from the closed low that gives the far west a glancing blow.
Could be some thunder with this elevated convection. Overall, did
not make too many changes to the going forecast.

&&

.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 342 PM EDT Sat May 25 2024

Active pattern for Upper Michigan continues in this forecasting
period. The long term pattern for Upper Michigan will start off with
an anomalous surface low and shortwave lifting northeast into the
Great Lakes Sunday and Monday. From there, broad mid-level troughing
establishes itself across the eastern half of North America before
ridging gradually builds into the region for the latter half of the
week and into the weekend. Together, these will yield early week
rain with cooler temperatures, followed by a dry period midweek and
warming temperatures late week.


After early morning rain showers pull out of the western UP, expect
one more brief period of dry weather through the morning ahead of an
approaching shortwave and deepening surface low ejecting out of the
Plains. This tracks somewhere between northern IL and southern WI by
Sunday evening, and will continue to move ENE into the Lower
Peninsula Sunday night through Monday before moving north of Lake
Huron and rapidly deepening by Monday evening. PWATS building to 1-
1.5 across the region coupled with increasingly strong dynamics
should yield widespread rain for Upper Michigan by Sunday afternoon,
persisting until the system pulls away Monday. QPF varies per model
given persistent subtle differences in track, but the general
thinking is widespread 0.5-1.5 inches of rain, with those most
likely to see the higher amounts being the central and eastern
portions of Upper Michigan. Precip should end west to east through
the day Monday, but another shortwave pressing eastward across
Minnesota/Wisconsin, followed by a more broad shortwave dropping
southeast out of Ontario/Manitoba Monday night may support shower
activity into Tuesday night. The best potential for additional
rainfall during this period will be across the eastern UP, closer in
proximity to the deep low to our northeast and the wraparound
moisture being directed into the area. High pressure and a dry
airmass builds into the region Wednesday and should maintain mostly
dry conditions for the forecast area to finish at least through
early Friday.

As the early week surface low pulls away, a cool airmass will rotate
into the region. Daytime temperatures on Tuesday/Wednesday look to
be in the 50s and 60s with overnight lows in the 40s and 30s. That
said, NBM 25th percentile shows temperatures dipping below 35F
across much of the interior UP by Thursday morning; with light winds
and a cool and very dry airmass, temperatures flirting with frost
advisory criteria are a good bet. Dewpoints, too, will be something
to watch during the midweek period. Dry and well-mixed soundings,
particularly Wednesday, could lead to plummeting dewpoints and RH
falling into the lower 30s%. A mitigating factor for the fire
weather risk, in addition to fairly light winds, will be the
widespread rain in the preceding days.

Ridge axis builds into the region Thursday night while another
trough presses out of the Rockies. Current thinking is for surface
high to maintain its spot over the region until the eastward
progressing trough shifts into the region. This could allow PoPs to
creep into the western UP as early as Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 146 PM EDT Sat May 25 2024

VFR cigs/vsby are expected to prevail at each terminal through this
TAF period, but showers and embedded thunderstorms are expected to
impact IWD/CMX this evening. Gusty southwest winds up to 25 kts
continue at IWD and up to 35 kts at CMX until wind profiles weaken
and surface heating subsides late this afternoon. Confidence in
thunder occuring is in the 50-75% range, justifying inclusion in
TAFs even though storms may not track directly over each terminal.
TAFs reflect the most likely outcome, which is a brief ~2-3 hour
period of shra/-tsra followed by a 12-15 hour dry period toward the
end of the TAF period. However, a weak frontal boundary lingering
nearby may be sufficient to trigger light rain showers throughout
Sunday morning at CMX/IWD. Showers are increasingly likely late in
the TAF period as a low pressure system lifts north toward Upper
Michigan with a period of light to moderate rain expected at all
terminals late on Sunday. SAW stays dry with VFR cigs/vsby
through tonight, but deteriorating cigs/vsbys are expected near
or shortly after the end of this TAF period.

&&

.MARINE...
Issued at 342 PM EDT Sat May 25 2024

Low pressure over the Ontario/Manitoba border continues to track
northward this afternoon while weakening. Winds remain elevated
across western Lake Superior, coming in out of the SW and continuing
to gust to around 20-25kts through the early evening while to the
east, SE winds are coming in at around 10 knots. Winds across the
western half of the lake fall below 20 knots later this evening.  A
slight chance of thunderstorms exists on and off throughout tonight
in the southern part of western Lake Superior, including the
Keweenaw, and lingering mid-lake into Sunday morning.

By early Sunday morning, weak high pressure building into the region
results in light southerly flow of less than 5-15 kt, backing to the
E/SE by mid-morning ahead of an approaching low over the Plains.
Waves fall to around 1-3ft. By early Sunday evening, winds are
forecasted to be easterly across Lake Superior at 10-15 kt. Winds
continue to back and build throughout Sunday night as the Colorado
low approaches, reaching northerly by Monday morning at 15-20 kt and
waves building to 3-5 ft. A slight chance of thunderstorms exists on
eastern Lake Superior very early Monday morning.

Backing continues until Monday night, when steady northwesterly flow
becomes established at 10-20 kt, being higher potentially up to
25kts in eastern Lake Superior. This northwesterly flow and wave
heights of 3-5 ft are expected to remain steady until Wednesday
midday when high pressure begins to build into the area. At this
time, expect light and variable winds and decreasing waves until
Thursday midday, when light southerly flow at 5-15 kt re-establishes
itself, along with waves 1-3 ft, for the remainder of the forecast
period.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...07
LONG TERM...LC
AVIATION...EK
MARINE...LC